1. Field of the Invention
The present invention is directed to a system for performing a two dimensional transform, such as a two dimensional Fourier transform and, more particularly, to a system that performs the transformation in parallel.
2. Description of the Related Art
Many problems in computer science, particularly image processing problems, require the processing of vary large amounts of data. For example, the Fourier transform of a two dimensional image to allow the edges of objects in the image to be located is a computationally intensive operation generally performed on special array processing computers. The transform takes a considerable amount of time to perform and the computers are very expensive. What is needed is a system that performs a two dimensional transform by performing the operations in parallel to reduce the time required. What is also needed is a system that is low in cost.
It is an object of the present invention to provide a system that performs a two dimensional transform very quickly by performing steps of the transform in parallel.
It is an additional object of the present invention to provide a system that can be created at lower cost than array processors.
It is also an object of the present invention to provide an optical processing device to perform a two dimensional transform.
The above objects can be attained by a system that optically performs complex transforms such as Fourier transforms. The system includes a pixel addressable spatial modulator that adjusts the phase of the light of each pixel. A transform lens, such as a Fourier lens, performs a two dimensional transform of the pixels"" outputs. The transformed outputs are sampled by a light detector and processed by a computer into the final transform.
The invention is an arrangement of optical and electronic devices, said arrangement capable of constructing and summing a finite series transformation of one function in terms of other functions.
These together with other objects and advantages which will be subsequently apparent, reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout.
In the basic configuration of the invention an amplitude beamsplitter divides an incoming beam into two usually equal portions. One portion enters the k0 circuit, the other enters the km,n circuit. The beam of the km,n circuit passes to a spatial light phase modulator designated SLM, where it is further spatially divided into a multiplicity of pixel beams. The spatial light modulator, SLM, controls the relative phase of these pixel beams which are all simultaneously directed to form an interference pattern on a surface. Aside from the temporal oscillation at optical frequencies, the amplitude of the electric and magnetic field as a function of the x and y coordinates along this surface is a portion of the sought-after sum of the series eigenfunction expansion of a function F(x, y).
The invention provides that an optical detector array may collect the pattern for further analysis and adaptation for viewing. The invention further directs the beam of the k0 circuit to said surface with such amplitude and phase as to add a bias field to the interference pattern. This bias field allows the use of square law detectors at said surface which otherwise cannot record the relative sign or phase of the field amplitudes within the pattern.
The invention provides methods by which all the portions may be produced separately on the surface and then added in a digital interface computer to produce F(x, y).
The invention is anticipated in particular for generating and summing Fourier eigenfunctions. However, adaptations within the invention provide the generation and summation of other functions as well.